The present invention relates to RFID systems and, in particular, it concerns a cost effective system that uses an array of Very Light Readers (VLR's) in which each VLR is based on an augmented RFID Tag circuit.
RF identification (RFID) systems are used to track objects, animals and/or people in a large range of applications. A general term for the application is Asset Management. RFID systems are radio communication systems that communicate between a radio transceiver, called a Reader, and a number of inexpensive devices called Tags. The Reader is also called “Interrogator” in the relevant literature.
An RFID system generally includes multiple Tags which are attached to objects (or assets) being monitored and one or more Readers which are used to communicate with the Tags. An encoder is optionally used to program the Tags with unique identification information.
In some of the RFID applications there is a need for real-time visibility and real time location tracking of assets or people inside a campus, building or a site like a hospital, construction site, factory or school. Prior art includes Readers installed in carefully designated places such that coverage is maintained over all the facility. The Readers are often capable of managing hundreds or even thousands of Tags. The prior art Readers are connected to a central server using wired or wireless data connections.
Location of Tags is performed in prior art systems using triangulation of the data from several Readers, or the use of received signal strength information (RSSI).
US Patent Application No. 2007/0207732, “RFID Reader architecture” to Rofougaran et al., discusses a low-cost Reader realized by providing a transmitter operable to generate an outbound radio frequency (RF) signal and a receiver operable to receive an inbound RF signal having a frequency similar to a frequency of the outbound RF signal on a single integrated circuit. Apparently, in this application, the Reader is a device which works with passive Tags; such Tags produce a back-scattering of the signal transmitted by the Reader.
US patent application 2007/0040681, “Low cost RFID system” to Jessup, also discusses a Reader (or “interrogator”) for passive Tags, where the Reader and system design comprises a low cost RFID system which allows individual Tags to be isolated, selected, programmed and verified.
US patent application no. 2007/0001813, “Multi-Reader coordination in an RFID system”, to Maguire et al. discusses a situation where multiple Readers cover a given volume. If multiple Readers broadcast at the same time, so-called “Reader collision” may occur. Reader collisions occur when the signals from two or more Readers overlap in time within the same or a proximate frequency band. The greater the number of Readers, the more likely Reader collision is to occur. Maguire et al. discloses a method of operating a plurality of Radio Frequency Identification Readers includes operating the Readers according to a spatial-division and time-division synchronization schedule.
US patent application no. 2008/0018455, “RFID modular Reader” to Kulakowski, discusses an RFID Reader for reading out and, optionally, recording information in non-contact RFID cards, using portable devises as the central unit, characterized by a modular structure, having a casing for the portable unit that contains a replaceable Reader module, connected thereto, along with the antennae. The characteristic feature of the Kulakowski is that the modularity enables it to interconnect with different mobile devices existing on the market, which lowers the price of the device and simplifies its software and usage.
Generally speaking, the prior art Readers are capable devices, but their price and size often require limiting the number deployed in a system in order to maintain a reasonable overall system cost, which in turn lowers the coverage abilities of the system. The requirement of serving large number of Tags in a large volume thereby requiring coverage of large distances may increase the cost of the Reader further. If the volume to be covered is divided into a number of sub-volumes such as a large facility with a number of small rooms, by non-limiting example, then the use of Readers usually capable of providing coverage for the size of the facility may still not provide adequate RF coverage due to RF attenuation caused by walls and ceilings.
There is therefore a need for a cost effective system that uses an array of Very Light Readers (VLR's) in which each VLR is based on an augmented RFID Tag circuit.